Volunteers fan out along a hillside during a weed eradication along Lobos Creek in San Francisco, Ca. on Wednesday March 7, 2012. The Golden Gate National Recreation Area, has over 35,000 Presidio Park Stewards, volunteering to work in the park.

Photo: Michael Macor, The Chronicle

Volunteers fan out along a hillside during a weed eradication along...

Image 2 of 5

Michael Chasse, (right center) natural resourse specialist with the GGNRA, points out the various plants found at the site, to volunteers during a weed eradication project along Lobos Creek in San Francisco, Ca. on Wednesday March 7, 2012. The Golden Gate National Recreation Area, has over 35,000 Presidio Park Stewards, volunteering to work in the park.

Volunteer, Dale Danley pulls up a non-native narrow leaf iceplant during a weed eradication along Lobos Creek in San Francisco, Ca. on Wednesday March 7, 2012. The Golden Gate National Recreation Area, has over 35, 000 Presidio Park Stewards, volunteering to work in the park.

Photo: Michael Macor, The Chronicle

Volunteer, Dale Danley pulls up a non-native narrow leaf iceplant...

Image 4 of 5

Volunteers fan out across a hillside during a weed eradication along Lobos Creek in San Francisco, Ca. on Wednesday March 7, 2012. The Golden Gate National Recreation Area, has over 35,000 Presidio Park Stewards, volunteering to work in the park.

Photo: Michael Macor, The Chronicle

Volunteers fan out across a hillside during a weed eradication...

Image 5 of 5

A volunteer at work during a weed eradication along Lobos Creek in San Francisco, Ca. on Wednesday March 7, 2012. The Golden Gate National Recreation Area, has over 35,000 Presidio Park Stewards, volunteering to work in the park.

On a windy weekday afternoon on the edge of spring, a crew of young people was digging holes on a bluff above the Golden Gate. It was a labor of love.

The crew, ranging from a musician turned ecologist to a high school student working toward his Eagle Scout badge, was helping to restore part of a coastal habitat in the Bay Area's biggest national park.

"I love doing this," said Eric Klein, 30, a onetime musician who is now a restoration ecologist with the Golden Gate National Parks Conservancy. "We are making a native grassland here. In two years or so, it will look here like it did in the 19th century, or before that."

The volunteers Klein leads are the foot soldiers in an effort to involve private citizens in hundreds of projects in the Golden Gate National Recreation Area, an 80,000-acre national park that extends from Tomales Bay to the coastal hills of San Mateo County.

On this day, he and the other members of the work crew were planting native bunchgrass on a bluff just west of Lincoln Boulevard in the Presidio. The idea was to replace invasive species, like ivy, or a former eucalyptus grove, planted years ago when the U.S. Army controlled the area.

Those plants just took over the bluff, changing it. Now crews supplied by the nonprofit conservancy are turning the area back to its natural state. They planted almost 300 small clumps of grass in an afternoon.

"It's a good way to help the community," said Leon Tang, 17, a student at George Washington High School in San Francisco. Leon was working on the project to help him earn his Eagle Scout badge. It was his first day as a Golden Gate conservancy volunteer.

An army of volunteers

The conservancy, which has been a partner with the National Park Service for more than 30 years, had 34,484 volunteers who put in 513,884 hours last year. That kind of work would cost $10.9 million on the open market, the conservancy says.

"They really do everything," said Greg Moore, executive director of the conservancy. "They grow native plants, they sell tickets, they band wild hawks in the Marin Headlands, they do historical restoration work, they volunteer at the flower gardens on Alcatraz."

Some volunteers have restored artillery gun bunkers in the Marin Headlands and now give tours, while others have rebuilt a Cold War-era Nike missile site just north of the Golden Gate. Other projects include work on the historic El Polin spring, an important artifact from the days when the Presidio was the farthest outpost of the Spanish colonial empire.

Work in the Presidio at such sites as El Polin and Lobos Creek is done by the Presidio Park Stewards, an affiliated organization in partnership with the conservancy, the National Park Service and the Presidio Trust, which administers the Presidio.

Bay Area's 'backyard'

Volunteers have built trails on the coast, counted fish in local creeks and worked on projects among the thousand-year-old trees in Muir Woods.

The volunteers range from retired folks to middle and high school students. "It's really all ages," Moore said. There is a paid, core staff, but for their effort, the volunteers get a pin or a hat, a T-shirt, maybe a water bottle, and an invitation to a once-a-year appreciation party.

"Their reward is the value they put in for the park," Moore said.

The Golden Gate National Recreation Area is an urban park, combining open country with parklands and beaches next to San Francisco and the cities of Marin and San Mateo counties.

"It's their backyard, and they want to take care of it," Denise Shea, associate director of volunteer management, said of the volunteers.

Over the past 30 years, the Golden Gate National Parks Conservancy has worked with the park service to make available more than 1,000 projects. The conservancy uses the Internet and social media sites such as Facebook, Twitter and Flickr to offer volunteer opportunities every day of the week, every week of the year.

In addition Moore and his top aides make sure the volunteers are aware their work is appreciated. It also doesn't hurt that the Golden Gate National Recreation Area includes some of the most beautiful areas in the country. This spring, the conservancy and its corps of volunteers will also be involved in the 75th anniversary celebration of the Golden Gate Bridge.

Volunteers also often meet after work to hang out in social programs.

"We have Tamale Saturdays," said Alex Hooker, who is the conservancy crew chief on several projects in San Francisco. His Saturday crew, which works at Lands End in San Francisco, heads to a Mexican restaurant in the Richmond District after a day's work.

Meeting new people

Many of the workers are new to the Bay Area and find that volunteering in the park is a good way to become familiar with the area and meet new people.

"The park here is very different from what I am used to," said Navit Reid, who is 24 and came to the Bay Area from Nebraska. She started as a volunteer and is now working as an intern for the conservancy. She is interested in a career path that might lead to working for the National Park Service. "We'll see what develops."

Another arm of the conservancy raises private funds for the park. The principal showpiece is Crissy Field, which was transformed back to a wetland 10 years ago with an $18 million gift from the Evelyn and Water Haas Jr. Fund, the largest cash gift ever to a national park.

Last year, about a million people came to Crissy Field, and 23,000 young people went through environmental education programs there. A lot of others did the grunt work: Volunteers filled 3,569 bags full of invasive vegetation in that corner of the Presidio.

"They want to have a connection with this park," Shea said, "because it is theirs."

How to volunteer

Information about becoming a volunteer in the Golden Gate National Recreation Area can be found at www.parksconservancy.org.